Slide core unit

ABSTRACT

The configuration is such that there are provided a slide core  21  ( 21 A) disposed to be movable toward and away from a cavity (molding space)  8   a  and driven at least in the direction toward the cavity  8   a  according to the closing action of a mold  8 , and a guiding member (guiding means)  11  ( 11 A) disposed at least on one mold member  7  of the mold and having a groove-shaped rail part  12   a  for supporting the slide core  21  in the directions toward and away from the cavity  8   a , wherein one member out of the slide core  21  and guiding means  11  is provided with urging means for urging the slide core relative to the guiding member  11  in the direction away from the cavity  8   a . This configuration makes it possible to reduce the size and the maintenance cost of the slide core.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of copending International Application No. PCT/JP03/04883, filed Apr. 17, 2003, and published in a non-English language.

TECHNICAL FIELD

The present invention relates to a slide core unit installed in a mold.

BACKGROUND ART

As a mold for use in an injection molding machine, what is illustrated in FIG. 19 a and FIG. 19 b is known, for instance. In this drawing, reference numeral 1 denotes a mold, which is configured as a paired structure provided with a stationary mold member 2 and a movable mold member 3. The stationary mold member 2 and the movable mold member 3 are respectively fixed to the stationary platen and the movable platen of an injection molding machine (not shown), for instance. A movement of the movable platen toward the stationary platen results in a closed state in which the movable mold member 3 is in contact with the stationary mold member 2, and a movement of the movable platen away from the stationary platen results in an open state in which the movable mold member 3 is away from the stationary mold member 2.

In the mold 1, when it is in the closed state, the respective mating faces 2 a and 3 a of the stationary mold member 2 and the movable mold member 3 are in a state of being tightly contacted to each other to form a cavity (molding space) 1 a which is to be filled with molten resin. Further, the mold 1 allows a molding A made of a resin solidified within the cavity 1 a to be taken out by opening the mold members.

However, if the molding A has an undercut A1 as shown in FIG. 19 a and FIG. 19 b, the part of the cavity 1 a corresponding to the undercut A1 will have to be formed in the core portion 4 a of a slide core 4. Incidentally, the core portion 4 a may be configured either integrally with or as a body separable from the slide core 4 to which the body can be attached and from which the body can be detached.

The slide core 4, by being installed in a groove-shaped rail portion 3 b in the movable mold member 3, is supported to be able to move toward and away from the cavity 1 a. The slide core 4 further has a slanted guide hole 4 b into which an angular pin 5 is to be inserted. The angular pin 5, fitted to the stationary mold member 2, is so configured as to obliquely protrude from the mating face 2 a.

In the same drawing, reference numeral 2 b denotes a locking block which, when the cavity 1 a is filled with highly pressurized resin, prevents the core portion 4 a from receding from the cavity 1 a; reference numeral 3 d, a stopper pin for holding the slide core 4 in a retreated position; and reference numeral 3 d, an ejector pin 3 d for separating the molding A from the cavity 1 a part.

In the mold 1 configured as described above, when it is closed as shown in FIG. 19 a, the angular pin 5 is inserted into the guide hole 4 b of the slide core 4, which is thereby moved toward the cavity 1 a and eventually the core portion 4 a constitutes a part of the cavity 1 a. Then, after the mold 1 is clamped, the cavity 1 a is filled with molten resin and, after the resin has solidified, the mold is opened as shown in FIG. 19 b.

When the mold is opened, the slide core 4 is moved by the angular pin 5 in the direction away from the cavity 1 a. As this brings the core portion 4 a into a state in which it is removed from the undercut A1 of the molding A, the molding A can be separated from the cavity 1 a part and taken out by operating the ejector pin 3 d.

There may be a case in which the slide core 4 is installed movably in the vertical direction. In this case, the slide core 4 in the state in which the mold is open is subject to a downward force by gravity, and to prevent a downward movement of the slide core 4 it is necessary to urge the slide core 4 all the time in the direction away from the cavity 1 a by providing the slide core 4 with a spring 3 e as shown in FIG. 20.

However, if the slide core 4 is provided with the spring 3 e, there will arise a problem that the size of the slide core 4 is enlarged, because a hole 4 c for embedding the spring 3 e has to be bored in the slide core 4. Moreover, as the groove-shaped rail portion 3 b for slidably supporting the slide core 4 is provided directly in the movable mold member 3, the whole movable mold member 3 has to be replaced when the rail portion 3 b has been worn out by the sliding movement of the slide core 4, resulting in a corresponding increase in the maintenance cost of the mold 1.

SUMMARY OF THE INVENTION

An object of the present invention, attempted in view of the circumstance described above, is to reduce the size of the slide core and the maintenance cost of the mold.

In order to solve the problem noted above, according to a first aspect of the invention, there is provided a slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein the slide core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from the molding space and driven in a forward direction toward the molding space at least in response to a closing action of the mold; and a guiding means installed on at least one of the mold members and supporting the slide core to be movable in the forward and backward directions toward and away from the molding space, and one member out of the slide core and the guiding means is provided with urging means for urging the slide core relative to the guiding means in a backward direction away from the molding space.

In a second aspect of the invention, the urging means comprises: a guide hole bored in the one member and extending in the forward and backward directions; a moving piece provided in the guide hole to be movable in the forward and backward directions; an elastic body provided in the guide hole and giving an elastic force to the moving piece; a long hole penetrating the other member, different from the one member, out of the slide core and the guiding means from within the guide hole and formed long in the forward and backward directions; and a pin which is inserted into the long hole and of which the base end is fixed to the moving piece and the tip protrudes toward the other member, and the other member is provided with a concave portion with which the tip of the pin is to engage, and the elastic body is disposed within the guide hole to urge the slide core in the backward direction with an elastic force working via the moving piece.

According to a third aspect of the invention, there is provided a slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state wherein the slide core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from the molding space and driven in a forward direction toward the molding space at least in response to a closing action of the mold; and a guiding means installed on at least one of the mold members and supporting the slide core to be movable in the forward and backward directions toward and away from the molding space, and the slide core is provided with urging means for urging the slide core relative to the guiding means in a backward direction away from the molding space.

In a fourth aspect of the invention, the urging means comprises: a guide hole bored in the slide core and extending in the forward and backward directions; a moving piece disposed in the guide hole to be movable in the forward and backward directions; an elastic body disposed in the guide hole to urge the moving piece in the forward direction toward the molding space; a long hole penetrating from inside the guide hole toward the guiding means and formed long in the forward and backward directions; and a pin which is inserted into the long hole and of which the base end is fixed to the moving piece and the tip protrudes toward the guiding means, and the guiding means is provided with a concave portion with which the tip of the pin is to engage.

According to a fifth aspect of the invention, there is provided a slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein the slide core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from the molding space and driven in a forward direction toward the molding space at least in response to a closing action of the mold; and a guiding means installed on at least one of the mold members and supporting the slide core to be movable in the forward and backward direction toward and away from the molding space, and the guiding means is provided with urging means for urging the slide core relative to the guiding means in a backward direction away from the molding space.

In a sixth aspect of the invention, the urging means comprises: a guide hole bored in the guiding means and extending in the forward and backward directions; a moving piece disposed in the guide hole to be movable in the forward and backward directions; an elastic body disposed in the guide hole to urge the moving piece in the backward direction; a long hole penetrating from inside the guide hole toward the guiding means and formed long in the forward and backward directions; and a pin which is inserted into the long hole and of which the base end is fixed to the moving piece and the tip protrudes toward the slide core, and the slide core is provided with a concave portion with which the tip of the pin is to engage.

In a seventh aspect of the invention, the mold member on which the guiding means is to be disposed is provided with a space between a rail portion movably supporting the slide core disposed in the guiding means and an outer end of the mold member to thereby permit the slide core to be inserted into the space.

In an eighth aspect of the invention, one of the slide core and the guiding means has a ball plunger for holding the slide core in its standby position away from the molding space to a prescribed extent with a greater force than an urging force of the urging means.

According to the invention, since the guiding means for guiding the slide core in the forward and backward directions is disposed on a mold member, even if the movements of the slide core have worn off the guiding means, only the guiding means will need to be replaced but not the mold member on which the guiding means is disposed. Accordingly, the maintenance cost of the mold can be reduced.

According to the invention, since the slide core can be urged with respect to the guiding means in the direction away from the molding space via the pin protruding from one member out of the slide core and the guiding means toward the other member, eventually an elastic force will work along the part where the slide core and the guiding means slide relative to each other. Accordingly, the slide core can be moved stably backward.

According to the invention, since the slide core is provided with urging means for urging the slide core in the backward direction with respect to the guiding means, it is possible to simplify and reduce the size of the structure of the guiding means. Accordingly, the cost of maintenance required for replacing the guiding means can be reduced.

According to the invention, though the moving piece disposed in the guide hole is urged toward the molding space by the elastic force of the elastic body, as the tip of the pin is engaged with the concave portion of the guiding means, the slide core is urged in the direction away from the molding space by the reactionary force in which the concave portion is to be a fulcrum. In this case again, since the elastic force works via the pin along the part where the slide core and the guiding means slide relative to each other, the slide core can be moved stably backward.

According to the invention, since there is disposed guiding means for guiding the slide core in the forward and backward directions and this guiding means is provided with urging means for urging the slide core in the backward direction, the slide core can be reduced in size compared with the prior art according to which the slide core is provided with a spring. Moreover, since there is no need to bore a hole in which to embed the spring, the machining of the slide core can be simplified correspondingly. Therefore, the manufacturing cost can be reduced, and at the same time the cost of maintenance required for replacing the slide core can be reduced.

According to the invention, since the urging means comprises a guide hole bored in the guiding means, a moving piece disposed in the guide hole to be movable in the forward and backward directions, an elastic body for urging the moving piece in the backward direction, a long hole penetrating from inside the guide hole toward the slide core, and a pin which is inserted into the long hole and of which the base end is fixed to the moving piece and the tip protrudes toward the slide core, wherein the tip of the pin is engaged with a concave portion in the slide core, the elastic force working from the elastic body on the moving piece can be brought to work on the slide core via the pin to move the slide core in the direction away from the molding space. In this case again, since the elastic force works via the pin along the part where the slide core and the guiding means slide relative to each other, the slide core can be moved stably backward.

According to the invention, since a space through which the slide core can be inserted is provided between the rail portion movably supporting the slide core in the guiding means and the outer end of the mold member, the slide core can be taken out of the rail portion in the guiding means in a state in which, for instance, the mold is opened. Therefore, when the slide core and the core part fitted to the slide core, for instance, need repair or replacement, the repair or replacement can be easily accomplished without having to remove the mold from the injection molding machine or the like.

According to the invention, since one of the slide core and the guiding means has a ball plunger for holding the slide core in its standby position away from the molding space to a prescribed extent with a greater force than the urging force of the urging means, the slide core does not come off the guiding means in normal opening or closing process, and the slide core can be taken off the guiding means by applying an external force greater than a prescribed magnitude. Therefore, because there is no need to use a tool for attaching the slide core to the guiding means or detaching the former from the latter, there is an advantage that the work to attach or detach the slide core is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a slide core unit in a first embodiment of the present invention;

FIG. 2 a and FIG. 2 b show a guiding member of the slide core unit, wherein FIG. 2 a showing a front view and FIG. 2 b, a plan;

FIG. 3 a through FIG. 3 d show the slide core of the slide core unit, wherein FIG. 3 a is a front view, FIG. 3 b, a side view, FIG. 3 c, a plan view and FIG. 3 d, a sectional view taken along line D—D in FIG. 3 b;

FIG. 4 a through FIG. 4 d show the angular cam of the slide core unit, wherein FIG. 4 a is a front view, FIG. 4 b, a side view, FIG. 4 c, a bottom view and FIG. 4 d, a sectional view taken along line D—D in FIG. 4 b;

FIG. 5 is a sectional view showing a state in which the slide core is removed from the guiding member in the slide core unit;

FIG. 6 is a sectional view of the essential part, showing urging means of the slide core unit;

FIG. 7 a and FIG. 7 b illustrate the principle of the moving of the slide core by the angular cam in the slide core unit, wherein FIG. 7 a showing the state before the slide core is driven and FIG. 7 b, after the slide core has been driven;

FIG. 8 is a sectional view of the slide core unit, showing a state after the stationary mold member and the movable mold member have been closed;

FIG. 9 is a sectional view of the slide core unit, showing a state after the stationary mold member and the movable mold member have been opened;

FIG. 10 is a sectional view of another example of guiding member in the slide core unit;

FIG. 11 is an expanded sectional view of the essential part of that another example;

FIG. 12 is an exploded perspective view of a slide core unit in a second embodiment of the present invention;

FIG. 13 a and FIG. 13 b show the guiding member of the slide core unit, wherein FIG. 13 a is a plan view and FIG. 13 b, a sectional view;

FIG. 14 a through FIG. 14 e show the slide core of the slide core unit, wherein FIG. 14 a is a front view, FIG. 14 b, a side view, FIG. 14 c, a plan view, FIG. 14 d, a bottom view and FIG. 14 e, a sectional view taken along line E—E in FIG. 14 b;

FIG. 15 is a sectional view showing a state in which the slide core is removed from the guiding member in the slide core unit;

FIG. 16 a and FIG. 16 b illustrate the principle of the moving of the slide core by the angular cam in the slide core unit, wherein FIG. 16 a showing the state before the slide core is driven and FIG. 16 b, showing the state after the slide core has been driven;

FIG. 17 is a sectional view of another example of guiding member in the slide core unit;

FIG. 18 a and FIG. 18 b show a slide core and an angular cam with a meshing structure different from that of the slide core and the angular cam in either of the slide core units in the first and second embodiments of the invention, wherein FIG. 18 a showing the state before the slide core is driven and FIG. 18 b, showing the state after the slide core has been driven;

FIG. 19 a and FIG. 19 b show a slide core unit cited as an example of the prior art, wherein FIG. 19 a is a sectional view showing a state after the stationary mold member and the movable mold member have been closed and FIG. 19 b, a sectional view showing a state after the stationary mold member and the movable mold member have been opened; and

FIG. 20 is a sectional view of a slide core unit cited as another example of the prior art.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment of the present invention will be described below with reference to FIG. 1 through FIG. 18 b.

First Embodiment

To begin with, a first embodiment will be described with reference to FIG. 1 through FIG. 9. Constituent elements in common with the prior art are denoted by respectively the same reference signs, and their description will be simplified.

A slide core unit 10 in this embodiment is to be installed in a mold 8 as shown in FIG. 8 and FIG. 9. The mold 8 is configured as a paired structure provided with a stationary mold member 6 and a movable mold member 7 configured to be openable and closable, and these stationary mold member 6 and movable mold member 7 are respectively fixed to the stationary platen and the movable platen of an injection molding machine (not shown). The injection molding machine drives the movable mold member 7 in the opening or closing direction by moving the movable platen away from or toward the stationary platen.

In the mold 8, as shown in FIG. 8, when it is in the closed state, the respective mating faces 6 a and 7 a of the stationary mold member 6 and the movable mold member 7 are in a state of being tightly contacted to each other to form a cavity (molding space) 8 a which is to be filled with molten resin. Further, the mold 8 allows a molding B made of a resin solidified within the cavity 8 a to be taken out by opening the mold members and sticking it out with an ejector pin 3 d as shown in FIG. 9.

The slide core unit 10 is provided with a guiding member (guiding means) 11 fixed to the movable mold member 7, which is one of the mold members, a slide core 21 supported by the guiding member 11 to be linearly movable, and an angular cam 31 fixed to the stationary mold member 6, which is the other mold member.

The guiding member 11, as shown in FIG. 1, FIG. 2 a and FIG. 2 b, has a guide base 12 formed in a quadrangular plate shape and two guide plates 13. The guide base 12 has a rail part 12 a formed in a groove shape in one of its face. The rail part 12 a is formed between guide stages 12 b and 12 b rising on the right and left sides of the guide base 12, each having a quadrangular sectional shape, and extending in parallel to each other, and the rail part 12 a has a bottom face 12 c and inner side faces 12 d extending in parallel to each other on the right and left sides of the bottom face 12 c. This rail part 12 a linearly guides the slide core 21.

Also in the guide base 12 are formed, as shown in FIG. 5, a guide hole 12 e linearly extending underneath the bottom face 12 c and in the central part of the bottom face 12 c in its widthwise direction, and a long hole 12 f penetrating from the bottom face 12 c to the guide hole 12 e (penetrating from within the guide hole 12 e to the slide core 21). The guide hole 12 e, having a circular sectional shape, is formed in a length spanning the guide base 12 from one end face to the vicinity of the other. The long hole 12 f is in the central part of the bottom face 12 c in its widthwise direction, and extends in the direction coaxial with the guide hole 12 e. The length in which a spring pin 17, to be described afterwards, being inserted into this long hole 12 f, can travel within the long hole 12 f in the lengthwise direction, is somewhat longer than the stroke S of the slide core 21 moved by an angular cam 31 to be described afterwards.

A moving piece 14 is inserted into the guide hole 12 e to be movable in the axial direction, and a coil spring (elastic body) 15 to urge the moving piece 14 toward the deepest side is also provided in the guide hole 12 e. The coil spring 15 is held in a compressed state by a blind screw 16 blocking the aperture of the guide hole 12 e, and urges the moving piece 14 toward the deepest side (in the direction away from the cavity 8 a) all the time. In the position of the long hole 12 f is also installed, as shown in FIG. 6, a spring pin (pin) 17 which is inserted into this long hole 12 f and of which the lower end (base) is fixed to a linking hole 14 a of the moving piece 14 and the upper end (tip) protrudes from the bottom face 12 c to a prescribed height (protruding toward the slide core 21).

There is provided urging means for urging the slide core 21 in the direction of retreating from the cavity 8 a relative to the guiding member 11. The urging means has the guide hole 12 e, the long hole 12 f, the moving piece 14, the coil spring 15, the blind screw 16 and the spring pin 17.

The linking hole 14 a is formed in a prescribed depth from the outer circumferential face of the columnar moving piece 14, and in its bottom is bored an ejection hole 14 b having a smaller diameter than that of the linking hole 14 a. Further in the guide base 12 is bored a through hole 12 g in a position which becomes coaxial with the ejection hole 14 b in a state in which the moving piece 14 has been moved by the coil spring 15 to the deepest part of the guide hole 12 e.

The spring pin 17 is placed in a state in which it protrudes from the bottom face 12 c by a prescribed height by being driven into the linking hole 14 a via the long hole 12 f, and is removed from the linking hole 14 a by being driven out with a rod-shaped jig from the through hole 12 g and the ejection hole 14 b.

Further in the guide base 12, a through hole 12 h spanning the guide base 12 from its other end face to the guide hole 12 e is bored coaxially with the guide hole 12 e. This through hole 12 h is smaller in diameter than the guide hole 12 e. Further in the moving piece 14 is formed a threaded hole 14 c, extending to orthogonally cross the linking hole 14 a, in a position in which this hole 14 c becomes coaxial with the through hole 12 h in a state in which the moving piece 14 is inserted into the guide hole 12 e, and in this threaded hole 14 c is provided a stop screw 16 a for securely fixing the spring pin 17 into the linking hole 14 a.

Incidentally, the through hole 12 h enables a jig, such as a screw driver (not shown), to be inserted to turn the stop screw 16 a to rotate.

The spring pin 17 can be placed in a state of being linked to the linking hole 14 a with sufficient firmness by merely being driven into the linking hole 14 a. Therefore, when the spring pin 17 is to be used, the threaded hole 14 c, the stop screw 16 a and the through hole 12 h can be dispensed with, though, when a parallel pin is used instead of the spring pin 17 and this parallel pin is inserted into the linking hole 14 a by ordinary loose fit instead of pressure fit, the threaded hole 14 c, the stop screw 16 a and the through hole 12 h are indispensable. Thus, where a parallel pin is used, the parallel pin can be securely fixed into the linking hole 14 a with the stop screw 16 a.

The guide base 12 is also provided, as shown in FIG. 2 a and FIG. 2 b, with a ball plunger 18 so arranged that its ball 18 a protrudes partly from one of the inner side faces 12 d. This ball plunger 18 is embedded into the guide base 12, fixed with a thread formed in the outer circumference of the body and urges the ball 18 a in the protruding direction with a coil spring 18 b provided within that body. The ball plunger 18 is so disposed that part of the ball 18 a protruding from the inner side face 12 d can engage with an engaging concave portion 21 g, to be described afterwards, of the slide core 21. The engagement of the ball 18 a with the engaging concave portion 21 g makes the force to inhibit the movement of the slide core 21 slightly greater than the force of the coil spring 15 to drive the slide core 21. The inhibitive force, however, is sufficiently smaller than the force of a fingertip operation by an average person for sliding the slide core 21.

The parts of guide, plates 13 protruding toward the rail part 12 a, as shown in FIG. 1, FIG. 2 a and FIG. 2 b, are enabled to slidably support the upper faces 21 f of ribs 21 d, to be described afterwards, of the slide core 21 by being fixed to the top faces of the right and left guide stages 12 b with bolts B1. These guide plates 13 can function to prevent the slide core 21 from rising above the bottom face 12 c of the rail part 12 a. The guide stages 12 b and the guide plates 13, after being positioned by at least two pins P, such as spring pins and parallel pins, arranged at prescribed intervals in the lengthwise direction, are coupled by the bolts B1.

In the guiding member 11 configured as described above, as shown in FIG. 8 and FIG. 9, the guide base 12 is to be fixed by being fitted into a concave portion 7 b formed in the mating face 7 a of the movable mold member 7, and the rail part 12 a, the guide hole 12 e and the long hole 12 f are oriented in the direction of moving toward and away from the cavity 8 a. Thus the guiding member 11 is to be so fixed to the movable mold member 7 as to guide the slide core 21 toward and away from the cavity 8 a.

Between the guiding member 11 in the movable mold member 7 and the outer end of the movable mold member 7, there is a face 7 c which is at the same level as or lower than the bottom face 12 c of the rail part 12 a in the guide base 12 fitted into the concave portion 7 b, and there is constituted a space 7 d into which the slide core 21 can be inserted.

The slide core 21, as shown in FIG. 1, FIG. 3 a through FIG. 3 d and FIG. 5, is formed in a substantially quadrangular pole having the bottom face 21 a, right and left faces 21 b and top face 21 c. The quadrangularly shaped bottom face 21 a and side end faces 21 e of ribs 21 d protruding to the right and left of the bottom face 21 a are slidably supported by the bottom face 12 c and the inner side faces 12 d of the rail part 12 a. Also, the upper faces 21 f of the right and left ribs 21 d are slidably supported by the guide plates 13. Further, in the side end face 21 e of the ribs 21 d is formed the arcuate engaging concave portion 21 g with part of the ball 18 a engages with.

Also, the slide core 21 has, in each of the right and left faces 21 b a concave portion 21 h into which a backward driving cam piece 31 c of the angular cam 31 to be described afterwards can be inserted. In the axial center of the slide core 21 is bored a through hole 21 i for a bolt B2 for fixing a core part 41, and in its other end face in the axial direction is formed a concave portion 21 j for alignment with the core part 41.

Further at the other end of the slide core 21 in its axial direction is formed a forward driven cam face 21 k. This forward driven cam face 21 k consists of a inclined face from the bottom face 21 a side to the top face 21 c, gradually positioned toward the core part 41. On the back sides of the right and left side edges of the forward driven cam face 21 k are formed backward driven cam faces 21 m. These backward driven cam faces 21 m are formed by the inner side faces of the concave portion 21 h in parallel with the forward driven cam face 21 k.

In the bottom face 21 a of the slide core 21 is formed a concave portion 21 n which engages with the upper end of the spring pin 17 protruding from the bottom face 12 c of the guide base 12. This concave portion 21 n, located at the center of the bottom face 21 a in its widthwise direction, linearly extends from a prescribed position on the forward driven cam face 21 k side to reach the end face toward the core part 41.

The slide core 21, configured as described above, is installed in the guiding member 11 in the movable mold member 7, with the core part 41 being fixed by means of the bolt B2 as shown in FIG. 8 and FIG. 9. In this state, the slide core 21 is supported to be movable toward and away from the cavity 8 a, and the forward driven cam face 21 k, positioned on the base end face of the slide core 21 on the side reverse to the cavity 8 a, is so inclined as to be positioned gradually closer to the cavity 8 a as it approaches the stationary mold member 6. Further, the slide core 21 is stopped in the standby position farthest away from the cavity 8 a as the ball 18 a of the ball plunger 18 engages with the engaging concave portion 21 g.

To the face 7 c of the movable mold member 7 where the slide core 21 is inserted or extracted is fixed a stopper bolt 19 for preventing the slide core 21 from coming off the guide base 12.

On the other hand, the angular cam 31, as shown in FIG. 1, FIG. 4 a through FIG. 4 d, and FIG. 7 a through FIG. 9, is integrally formed of a base portion 31 a fixed to the stationary mold member 6, a forward driving cam portion 31 b provided at the end in the direction away from the cavity 8 a, and the backward driving cam pieces 31 c and 31 c arranged on the right and left.

The face of the forward driving cam portion 31 b toward the cavity 8 a constitutes a forward driving cam face 31 d. This forward driving cam face 31 d is inclined in the same direction as the forward driven cam face 21 k of the slide core 21 installed in the movable mold member 7. When closing the mold, the slide core 21 is driven toward the cavity 8 a by the stroke S (see FIG. 7 a) by sliding the forward driving cam face 31 d in contact with the forward driven cam face 21 k. In the completely closed state of the mold, the forward driving cam face 31 d acts to protrude the tip of the core part 41 to the part corresponding to the undercut B of the molding B in the cavity 8 a. In the closed state of the mold, the forward driving cam portion 31 b also functions as a locking block to prevent the core part 41 from moving away from the cavity 8 a.

On the other hand, the right and left backward driving cam pieces 31 c are so formed as to be inserted into the respectively right and left concave portions 21 h of the slide core 21 when the mold is to be closed, and the tips of their sides along the forward driving cam face 31 d constitute backward driving cam faces 31 e. However, since the slide core 21 is urged by urging means in the direction away from the cavity 8 a, normally the backward driving cam faces 31 e is slightly away from the backward driven cam faces 21 m.

In the base portion 31 a is bored a through hole 31 f through which a bolt B3 is to be inserted. The angular cam 31 is fixed to the stationary mold member 6 by the bolt B3 in a state in which its base portion 31 a is fitted into a concave portion 6 b of the stationary mold member 6.

In the slide core unit 10 configured as described above, the guiding member 11 is provided for guiding the slide core 21 in the directions toward and away from the cavity 8 a, and this guiding member 11 is provided with urging means which, consisting of the guide hole 12 e, the moving piece 14, the coil spring 15, the blind screw 16 and the spring pin 17 urges the slide core 21 away from the cavity 8 a. Therefore, downsizing of the slide core 21 can be established relative to the slide core according to the prior art having a spring. When the slide core 21 is to be modified or replaced with another core of a different shape, only the slide core 21 needs to be modified or replaced, and nothing pertaining to the urging means or the like needs to be modified or replaced, resulting in a saving in modifying cost or the labor and cost required for redesigning and machining the shape. Therefore the costs of maintenance and manufacture can be reduced.

As the urging means also applies, with the spring pin 17 protruding from the bottom face 12 c of the rail part 12 a in the guide base 12, urging force to the concave portion 21 n of the bottom face 21 a in the slide core 21, it can stably slide the slide core 21 along the bottom face 12 c with that urging force. Thus, it can securely prevent the movement of the slide core 21 from becoming intermittent or stopping.

Further, as there is provided, between the guide base 12 and the outer end of the movable mold member 7, the space 7 d to make possible insertion of the slide core 21, the slide core 21 having the core part 41 can be taken out of the rail part 12 a of the guiding member 11 as indicated by an arrow in FIG. 5 in a state in which the mold is open, for instance. Therefore, when the slide core 21 or the core part 41 needs repair, it can be easily done without having to remove the mold 8 from the injection molding machine.

Also as the guiding member 11 is provided with the ball plunger 18 for holding the slide core 21 in the standby position away from the cavity 8 a to a prescribed extent, the slide core 21 does not come off the guiding member 11 in a normal opening or closing process, and the slide core 21 can be readily taken off the guiding member 11 by working an external force of not smaller than a prescribed strength. Therefore, since any tool need not be used for attaching the slide core 21 to, or detaching it from, the guiding member 11, there is an advantage of a simplified attaching/detaching procedure.

Incidentally, although the guiding member 11 in the first embodiment of the invention described above consists of the guide base 12 and the guide plates 13 separable from each other, this guiding member 11 can as well consist of the guide base 12 and the guide plates 13 formed integrally. In this case, the rail part 12 a is formed in a U shape by wire cutting or otherwise. This integrated structure would provide an advantage of reducing the number of parts corresponding to that integration and of reducing the numbers of such parts as the bolts B1 and the pins P as well.

Further, although the guide hole 12 e is so formed as to span the guide base 12 from one end face to the vicinity of the other end face, this guide hole 12 e may as well span the guide base 12 from that second end face to the vicinity of the first end face as shown in FIG. 10 and FIG. 11.

In this latter case, not only can the moving piece 14 be inserted into the guide hole 12 e from the second end face but also can a jig, such as a screw driver, be inserted from that second end face to tighten the stop screw 16 a (see FIG. 11), and accordingly there is an advantage that the blind screw 16 and the through hole 12 h mentioned above can be dispensed with, resulting in a corresponding cost saving.

Second Embodiment

Next will be described a second embodiment of the present invention with reference to FIG. 12 through FIG. 16 b. Constituent elements in common with the first embodiment are denoted by respectively the same reference signs, and their description will be simplified.

A slide core unit 10A in this embodiment is so configured that a slide core 21A is provided with urging means for urging the slide core 21A onto the guiding member 1A in the direction away from the cavity 8 a.

The guiding member 11A is formed in a quadrangular pole as shown in FIG. 12, FIG. 13 a and FIG. 13 b, and in a top face 11 a, which is one of its faces, is formed a groove-shaped rail portion 11 b linearly extending in the axial direction. The rail portion 11 b has inner side faces 11 d rising vertically from both ends of the bottom face 11 c, formed in a planar shape, in the width direction, and on the parts along the top face 11 a in the inner side faces 11 d are formed protruding strips 11 e protruding inside toward each other and each having a rectangular section. The bottom face 11 c of the rail portion 11 b is formed in parallel with the top face 11 a.

In the bottom face 11 c of the rail portion 11 b is formed a concave portion 11 f which engages with the tip of the spring pin 17 protruding from the bottom end face 21 q, to be described afterwards, of the slide core 21A. This concave portion 11 f positioned in the central part of the bottom face 11 c in the widthwise direction, is formed of a groove linearly extending from one end face toward the other end face of the guiding member 11A. The other end functions as a stopper to stop the spring pin 17 by engagement.

Further, the guiding member 11A is provided, as shown in FIG. 13 a and FIG. 13 b, with a ball plunger 18 so arranged as to have part of a ball 18 a protrude from the bottom face 11 c. The ball 18 a protrudes toward one side of the linearly extending concave portion 11 f and engages with an engaging concave portion 21 u of the slide core 21A to be described afterwards.

The ball 18 a also functions to inhibit the slide core 21A from moving by engaging the engaging concave portion 21 u, and its inhibitive force is slightly greater than the force to drive the slide core 21A with the coil spring 15 to be described afterwards, though sufficiently smaller than the force by which an average person can slide the slide core 21A with his or her finger.

Further in the guiding member 11A are formed two screw holes 11 h and 11 i extending from the bottom face 11 g, which is another face positioned opposite the top face 11 a, toward the bottom face 11 c of the rail portion 11 b. These screw holes 11 h and 11 i are used for fixing the guiding member 11A itself into the concave portion 7 b of the movable mold member 7 with bolts. One screw hole 11 h penetrates the bottom face 11 c, while the other screw hole lli is discontinued without reaching the bottom face 11 c. The former screw hole 11 h functions as a screw hole for use in removing from the concave portion 7 b of the movable mold member 7 with the guiding member 11A in a state of being fitted into the concave portion 7 b.

The guiding member 11A configured as described above, as shown in FIG. 15, is fitted into the concave portion 7 b formed in the mating face 7 a of the movable mold member 7, and fixed to the movable mold member 7 with bolts (not shown) screwed into the screw holes 11 h and lli. In this fixed state, the other end face of the guiding member 11A is positioned toward the cavity 8 a, and the rail portion 11 b and the concave portion 11 f extend in the direction of moving toward or away from the cavity 8 a. Thus, the guiding member 11A is fixed to the movable mold member 7 to guide the slide core 21A in the direction of moving toward or away from the cavity 8 a.

The slide core 21A, as shown in FIG. 12 and FIG. 14 a through FIG. 16 b, is formed in a substantially quadrangular pole having the bottom face 21 a, the right and left faces 21 b and the top face 21 c, though it is not provided with the ribs 21 d (see FIG. 3 b) mentioned above, and instead is provided with, underneath the bottom face 21 a, a guided portion 21 p which engages with the rail portion 11 b of the guiding member 11A.

This guided portion 21 p has a bottom end face 21 q which slides along the bottom face 11 c of the rail portion 11 b, and further has engaged portions 21 r extending from both ends of this bottom end face 21 q in the widthwise direction and formed along the inner side faces 11 d and the protruding strips 11 e of the rail portion 11 b.

In the slide core 21A, there are also formed a guiding hole 21 s linearly extending in the central part of the guided portion 21 p in the widthwise direction along the axis and a long hole 21 t penetrating the bottom end face 21 q from within the guiding hole 21 s (that is, penetrating from the guiding hole 21 s toward the guiding member 11A). The guiding hole 21 s, having a circular sectional shape, is formed to span the slide core 21A from one end face to the vicinity of the other end face. The long hole 21 t, positioned at the center of the bottom end face 21 q in its widthwise direction, extends in the direction coaxial with the guiding hole 21 s.

The guiding hole 21 s is inserted into the moving piece 14 to be movable in the axial direction, and is provided with a coil spring (elastic body) 15 to urge the moving piece 14 toward the opening side of the guiding hole 21 s (toward the cavity 8 a). Into the long hole 21 t is inserted a spring pin (pin) 17 of which the base end is fixed to the linking hole 14 a of the moving piece 14 and the tip protrudes from the bottom end face 21 q by a prescribed length. The coil spring 15 is held in a compressed state by the bottom of the guiding hole 21 s and the moving piece 14 when the movement of the moving piece 14 is stopped by the engagement of the spring pin 17 with one end (the end toward the cavity 8 a) of the long hole 21 t, thereby urges the moving piece 14 toward the opening side of the guiding hole 21 s all the time.

Incidentally, the guiding hole 21 s, the long hole 21 t, the moving piece 14, the coil spring 15 and the spring pin 17 constitute urging means which urges the slide core 21A relative to the guiding member 11A in the direction of retreating from the cavity 8 a. The length by which the spring pin 17, to be described afterwards, inserted into the long hole 21 t can move in the long hole 21 t in the lengthwise direction is slightly longer than the stroke S of the slide core 21A (see FIG. 16 a) moved by the angular cam 31.

In the bottom end face 21 q of the slide core 21A are formed engaging concave portions 21 u to engage with the ball 18 a protruding from the bottom face 11 c of the rail portion 11 b. These engaging concave portions 21 u are so positioned that one of them is engaged with the ball 18 a in a state in which one end of the guided portion 21 p of the slide core 21A in the axial direction is inserted into one end of the rail portion 11 b of the guiding member 11A in the axial direction, the spring pin 17 is engaged with the other end of the concave portion 11 f and the spring pin 17 is engaged with one end of the long hole 21 t. The engaging concave portions 21 u are located in the corresponding opposite sides of the linearly extending concave portion 11 f, and engages with the ball 18 a of the ball plunger 18 on whichever side of the extending concave portion 11 f the ball plunger 18 may be positioned.

The slide core 21A configured as described above, with its core part 41 fixed with the bolt B2 is installed in the guiding member 11A in the movable mold member 7 as shown in FIG. 15. When it is installed, with the core part 41 being directed toward inside the movable mold member 7, the guided portion 21 p is inserted into the rail portion 11 b of the guiding member 11A. Then almost as soon as the tip of the spring pin 17 engages with the other end of the concave portion 11 f, the engaging concave portion 21 u engages with the ball 18 a. This results in a state in which the slide core 21A is held in the standby position, farthest away from the cavity 8 a.

In this state, the slide core 21A is supported to be movable in the direction toward or away from the cavity 8 a, while the forward driven cam face 21 k is positioned at the base end of the slide core 21A on the opposite side of the cavity 8 a and inclined to be positioned gradually toward the cavity 8 a as it approaches the stationary mold member 6 (see FIG. 9).

In the slide core unit 10A configured as described above, when the movable mold member 7 (see FIG. 15) is moved from the open state of FIG. 16 a to the closed state of FIG. 16 b, the forward driving cam face 31 d of the angular cam 31 comes into contact with the forward driven cam face 21 k of the slide core 21A to thereby move the slide core 21A toward the cavity 8 a (see FIG. 15) by the stroke S. Since the tip of the spring pin 17 is kept at halt by its engagement with the other end of the concave portion 11 f, the coil spring 15 undergoes compressive deformation as the slide core 21A moves toward the cavity 8 a.

When the movable mold member 7 moves from the closed state of FIG. 16 b to the open state of FIG. 16 a, the elastic force of the coil spring 15 moves the slide core 21A in the direction away from the cavity 8 a, and the engagement of one of the engaging concave portions 21 u with the ball 18 a of the ball plunger 18 stops the slide core 21A from moving farther. When this takes place, the spring pin 17 comes into contact with one end of the long hole 21 t. Therefore, in a state in which one of the engaging concave portions 21 u is engaged with the ball 18 a, the elastic force of the coil spring 15 does not work on the engaging part between the engaging concave portion 21 u and the ball 18 a. This is also true of the first embodiment.

Therefore, the same effect is provided in the second embodiment as in the first embodiment. In addition, the overall size of the slide core unit 10A provided with the slide core 21A, the guiding member 11A and the urging means can be reduced because the guided portion 21 p of the slide core 21A can be used as the space of accommodating the urging means.

Incidentally, while the guiding member 11A is configured to be fixed to the movable mold member 7 by screwing bolts into the screw holes 11 h and 11 i from underneath the movable mold member 7 according to the foregoing description, this guiding member 11A may as well be fixed to the movable mold member 7 by screwing second bolts into screw holes (not shown) of the movable mold member 7 from above the guiding member 11A as shown in FIG. 17.

Thus, the guiding member 11A may as well be provided with facing holes 11 j and 11 j opening in the bottom face 11 c of the rail portion 11 b over the screw holes 11 h and 11 i, and be fixed to the movable mold member 7 with the second bolts inserted to engage their heads with these facing holes 11 j. In this case, the diameter of the threaded portions of the second bolts would be smaller than that of the screw holes 11 h and 11 i so that the second bolts could move within the screw holes 11 h and 11 i in the axial direction, and each of the facing holes 11 j would have a right size to accommodate the head of each second bolt.

The above-described configuration enables the guiding member 11A to be attached to and detached from the mating face 7 a side of the movable mold member 7. Since it is therefore possible to replace the guiding member 11A without having to remove the mold 8 from the injection molding machine, the efficiency of molding can be improved. Further, as the guiding member 11A can as well be fixed to the movable mold member 7 by screwing bolts into the screw holes 11 h and 11 i from underneath, the freedom of fixing the guiding member 11A to the movable mold member 7 can be increased.

The meshing structure between the slide core 21 or 21A and the angular cam 31 with reference to the first or second embodiments, respectively, may as well be configured as illustrated in FIG. 18 a and FIG. 18 b. Thus, the slide core 21 or 21A can have a concave groove 21 v formed slantwise, and the angular cam 31 may have a protruding strip 31 g which can be inserted into and have a shape matching the concave groove 21 v.

In this case, the concave groove 21 v extends in the direction perpendicularly penetrating the sheet of FIG. 18 a and FIG. 18 b, and one of its mutually opposite faces (the face toward the cavity 8 a (see FIG. 15)) constitutes the forward driven cam face 21 k and the other face constitutes the backward driven cam face 21 m. The forward driven cam face 21 k and the backward driven cam face 21 m are inclined to be gradually positioned toward the cavity 8 a as they approach the stationary mold member 6 (see FIG. 9).

On the other hand, the protruding strip 31 g, like the concave groove 21 v, extends in the direction perpendicularly penetrating the sheet of FIG. 18 a and FIG. 18 b, and one of its fades in a back-to-back opposed relation with each other constitutes the forward driving cam face 31 d while the other constitutes the backward driving cam face 31 e. Further in FIG. 18 a and FIG. 18 b, reference numeral 21 x denotes screw holes bored in the slide core 21 or 21A to be used for fixing the slide core 21 or 21A to the movable mold member 7, and reference numeral 31 h, a screw hole bored in the angular cam 31 to be used for fixing the angular cam 31 to the stationary mold member 6.

In the above-described version of slide core unit 10 or 10A having the concave groove 21 v and the protruding strip 31 g, when the movable mold member 7 is moved from the open state of FIG. 18 a to the closed state of FIG. 18 b, the forward driving cam face 31 d of the angular cam 31 comes into contact with the forward driven cam face 21 k of the slide core 21 or 21A, and causes the slide core 21 or 21A to move toward the cavity 8 a by the stroke S. Or when the movable mold member 7 moves from the state of FIG. 18 b to that of FIG. 18 a, while the forward driving cam face 31 d and the forward driven cam face 21 k keep the state of being in contact with each other, the elastic force of the coil spring 15 in the urging means described above causes the slide core 21 or 21A to move in the direction away from the cavity 8 a. Incidentally, where no urging means is provided, the backward driving cam face 31 e of the angular cam 31 comes into contact with the backward driven cam faces 21 m of the slide core 21 or 21A to cause the slide core 21 or 21A to move in the direction away from the cavity 8 a.

As in the version of slide core unit 10 or 10A configured as described the structures of the concave groove 21 v and the protruding strip 31 g are very simple and compact, the slide core 21 or 21A and the angular cam 31 can be simplified and reduced in size.

INDUSTRIAL APPLICABILITY

As heretofore described, according to the invention, since the guiding means for guiding the slide core in the forward and backward directions is disposed on a mold member, even if the movements of the slide core have worn off the guiding means, only the guiding means will need to be replaced but not the mold member on which the guiding means is disposed. Accordingly, the maintenance cost of the mold can be reduced.

According to the invention, since the slide core can be urged with respect to the guiding means in the direction away from the molding space via the pin protruding from one member out of the slide core and the guiding means toward the other member, eventually an elastic force will work along the part where the slide core and the guiding means slide relative to each other. Accordingly, the slide core can be moved stably backward.

According to the invention, since the slide core is provided with urging means for urging the slide core in the backward direction with respect to the guiding means, it is possible to simplify and reduce the size of the structure of the guiding means. Accordingly, the cost of maintenance required for replacing the guiding means can be reduced.

According to the invention, though the moving piece disposed in the guide hole is urged toward the molding space by the elastic force of the elastic body, as the tip of the pin is engaged with the concave portion of the guiding means, the slide core is urged in the direction away from the molding space by the reactionary force in which the concave portion is to be a fulcrum. In this case again, since the elastic force works via the pin along the part where the slide core and the guiding means slide relative to each other, the slide core can be moved stably backward.

According to the invention, since there is disposed guiding means for guiding the slide core in the forward and backward directions and this guiding means is provided with urging means for urging the slide core in the backward direction, the slide core can be reduced in size compared with the prior art according to which the slide core is provided with a spring. Moreover, since there is no need to bore a hole in which to embed the spring, the machining of the slide core can be simplified correspondingly. Therefore, the manufacturing cost can be reduced, and at the same time the cost of maintenance required for replacing the slide core can be reduced.

According to the invention, since the urging means comprises a guide hole bored in the guiding means, a moving piece disposed in the guide hole to be movable in the forward and backward directions, an elastic body for urging the moving piece in the backward direction, a long hole penetrating from inside the guide hole toward the slide core, and a pin which is inserted into the long hole and of which the base end is fixed to the moving piece and the tip protrudes toward the slide core, wherein the tip of the pin is engaged with a concave portion in the slide core, the elastic force working from the elastic body on the moving piece can be brought to work on the slide core via the pin to move the slide core in the direction away from the molding space. In this case again, since the elastic force works via the pin along the part where the slide core and the guiding means slide relative to each other, the slide core can be moved stably backward.

According to the invention, since a space through which the slide core can be inserted is provided between the rail portion movably supporting the slide core in the guiding means and the outer end of the mold member, the slide core can be taken out of the rail portion in the guiding means in a state in which, for instance, the mold is opened. Therefore, when the slide core and the core part fitted to the slide core, for instance, need repair or replacement, the repair or replacement can be easily accomplished without having to remove the mold from the injection molding machine or the like.

According to the invention, since one of the slide core and the guiding means has a ball plunger for holding the slide core in its standby position away from the molding space to a prescribed extent with a greater force than the urging force of the urging means, the slide core does not come off the guiding means in normal opening or closing process, and the slide core can be taken off the guiding means by applying an external force greater than a prescribed magnitude. Therefore, because there is no need to use a tool for attaching the slide core to the guiding means or detaching the former from the latter, there is an advantage that the work to attach or detach the slide core is simplified. 

The invention claimed is:
 1. A slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein said slide core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from said molding space and driven in a forward direction toward said molding space at least in response to a closing action of said mold; and guiding means installed on at least one of said mold members and supporting said slide core to be movable in the forward and backward directions toward and away from said molding space, and one member out of said slide core and said guiding means is provided with urging means for urging said slide core relative to said guiding means in a backward direction away from said molding space, said urging means comprising a guide hole bored in said one member and extending in the forward and backward directions, a moving piece provided in said guide hole to be movable in the forward and backward directions, an elastic body provided in said guide hole and giving an elastic force to said moving piece, a long hole penetrating the other member, different from said one member, out of said slide core and said guiding means from within said guide hole and formed long in the forward and backward directions, and a pin which is inserted into said long hole and of which the base end is fixed to said moving piece and the tip protrudes toward said other member, and said other member is provided with a concave portion with which the tip of said pin is to engage, and said elastic body is disposed within said guide hole to urge said slide core in the backward direction with an elastic force working via said moving piece.
 2. A slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein said slide core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from said molding space and driven in a forward direction toward said molding space at least in response to a closing action of said mold; and guiding means installed on at least one of said mold members and supporting said slide core to be movable in the forward and backward directions toward and away from said molding space, and said slide core is provided with urging means for urging said slide core relative to said guiding means in a backward direction away from said molding space, said urging means comprising a guide hole bored in said slide core and extending in the forward and backward directions, a moving piece disposed in said guide hole to be movable in the forward and backward directions, an elastic body disposed in said guide hole to urge said moving piece in the forward direction toward said molding space, a long hole penetrating from inside said guide hole toward said guiding means and formed long in the forward and backward directions and a pin which is inserted into said long hole and of which the base end is fixed to said moving piece and the tip protrudes toward said guiding means, and said guiding means is provided with a concave portion with which the tip of said pin is to engage.
 3. A slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein said side core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from said molding space and driven in a forward direction toward said molding space at least in response to a closing action of said mold; and guiding means installed on at least one of said mold members and supporting said slide core to be movable in the forward and backward direction toward and away from said molding space, and said guiding means is provided with urging means for urging said slide core relative to the guiding means in a backward direction away from said molding space, said urging means comprising a guide hole bored in said guiding means and extending in the forward and backward directions, a moving piece disposed in said guide hole to be movable in the forward and backward directions, an elastic body disposed in said guide hole to urge said moving piece in the backward direction, a long hole penetrating from inside said guide hole toward said guiding means and formed long in the forward and backward directions, and a pin which is inserted into said long hole and of which the base end is fixed to said moving piece and the tip protrudes toward said slide core, and said slide core is provided with a concave portion with which the tip of said pin is to engage.
 4. The slide core unit according to claim 3, wherein said mold member on which said guiding means is to be disposed is provided with a space between a rail portion movably supporting the slide core disposed in said guiding means and an outer end of the mold member to thereby permit said slide core to be inserted into said space.
 5. The slide core unit according to claim 4, wherein one of said slide core and said guiding means has a ball plunger for holding said slide core in its standby position away from said molding space to a prescribed extent with a greater force than an urging force of said urging means.
 6. The slide core unit according to claim 3, wherein one of said slide core and said guiding means has a ball plunger for holding said slide core in its standby position away from said molding space to a prescribed extent with a greater force than an urging force of said urging means.
 7. A slide core unit to be installed in a mold configured to be openable and closable and having at least a pair of mold members which form a molding space when in a closed state, wherein said side core unit comprises: a slide core disposed to be movable in forward and backward directions toward and away from said molding space and driven in a forward direction toward said molding space at least in response to a closing action of said mold; guiding means installed on at least one of said mold members and supporting said slide core to be movable in the forward and backward direction toward and away from said molding space, and said guiding means is provided with urging means for urging said slide core relative to the guiding means in a backward direction away from said molding space, and one of said slide core and said guiding means has a ball plunger for holding said slide core in its standby position away from said molding space to a prescribed extent with a greater force than an urging force of said urging means.
 8. The slide core unit according to claim 2, wherein said mold member on which said guiding means is to be disposed is provided with a space between a rail portion movably supporting the slide core disposed in said guiding means and an outer end of the mold member to thereby permit said slide core to be inserted into said space.
 9. The slide core unit according to claim 2, wherein one of said slide core and said guiding means has a ball plunger for holding said slide core in its standby position away from said molding space to a prescribed extent with a greater force than an urging force of said urging means.
 10. The slide core unit according to claim 1, wherein said mold member on which said guiding means is to be disposed is provided with a space between a rail portion movably supporting the slide core disposed in said guiding means and an outer end of the mold member to thereby permit said slide core to be inserted into said space.
 11. The slide core unit according to claim 1, wherein one of said slide core and said guiding means has a ball plunger for holding said slide core in its standby position away from said molding space to a prescribed extent with a greater force than an urging force of said urging means. 